‘Five-color flag’, another use is to indicate orientation
One troop was divided into five sections, East, West, South, North and middle
For example, the north team of the troop (Alpha team),its troop flag used black background, west team of the troop(Beta team) should use white color for their troop flag. Alpha or Beta team it also includes five squads. Yellow flags for each central squad, red for each south squad.
Even the smallest unit had five color flags, and had the flag of its superior unit depending on where the unit was located at that time. So the army looked like countless colorful flags stretch as far as eye can see.
Commander in chief's banner
I chose the central orientation, so I used yellow, the text above’三军司命‘was three group's marshal.
On Dec 25, Ming’s offensive Japanese army commander-in-chief Li Rusong(李如松1549 -1598.5.
ordered deputy general Yang Yuan (杨元 15??-1598) as central group commander; deputy general Li Rubai (李如柏 1553 - 1619 younger brother of Li Rusong) as left group commander; deputy general Zhang Shijue (张世爵 15?? - ????) as right group commander, led thirty thousand troops mighty crossed the Yalu River opened the journey to rescue Korea.
Commander in chief's signal flag
The color was random to prevent giving away secrets beforehand
Banners in a museum in South Korea.